1. Field of the Invention
The present invention relates to anchors which are used for holding a filter underdrain block in a water or wastewater treatment filter of an underdrain system.
2. Description of Related Art
Anchors specifically suited for embedment in grout, between filter underdrain blocks on the bottom of water and wastewater treatment filters, are well known. Grout is used to fill the space between two rows of interconnected underdrain blocks, known as underdrain laterals.
FIG. 1 shows a prior art anchor rod 2 installed in a filter floor 12 adjacent an underdrain block 14 of an underdrain system 4. Referring to FIG. 1, the underdrain block 14 spans a channel or flume 16, which channel 16 is used to introduce backwash water to the underdrain block 14, is well known in the art. The underdrain block 14 has lugs 18 on a side thereof for securing the underdrain block 14 in a bed of grout G. Generally, the prior art anchor rod 2 consists of a single bent steel-reinforcing rod made in the shape of a “U”. The prior art U-shaped anchor rod 2 has spaced apart vertical legs 6 and a horizontal bar 8 defined therebetween, wherein the legs 6 extend downwardly and are embedded in the grout G between adjacent underdrain laterals, and secured to the filter floor 12. The filter floor 12 is typically made of either concrete or steel. More specifically, the U-shaped anchor rod 2 is typically located over the channel 16 (flume) in the filter floor 12, but can be located anywhere in the filter floor 12, which channel 16 allows backwash water to flow into openings in a bottom of the underdrain that span the channel 16. Because of the water pressure exerted against the bottom of the underdrain, and from water entering the underdrain out of the channel anchors such as the prior art U-shaped anchor rod 2 are required to hold the underdrain down. The horizontal bar 8 of the U-shaped rod 2 must be above the lugs 18 in the grout G in order to put the grout G between the horizontal bar 8 and the lugs 18 in compression. This is the most effective location for hold-down strength against uplifting forces.
There are several drawbacks to the prior art one piece U-shaped anchor rod 2. First, the underdrain must be installed level regardless of variations in the floor elevation. In situations where the underdrain is at a higher elevation over the channel or other locations on the filter floor, the fixed vertical dimension of the anchor rod 2 makes it impossible to maintain both a minimum embedment or attachment of the vertical legs 6, while at the same time assuring correct elevation of the horizontal bar 8 relative to the lugs 18 of the underdrain system 4. Second, if the vertical legs 6 of the anchor rod 2 are made extra long to accommodate variable elevations, sometimes the legs 6 will have to be cut or holes made deeper in the filter floor 12. Third, the prior art anchor rod 2 does not allow the vertical legs 6 to be rotated when installed using an adhesive, which is preferred by adhesive manufacturers for proper installation of the U-shaped rods.
It is an object of the present invention to overcome the aforesaid drawbacks of the prior art anchor rod 2. Particularly, it is an object of the invention to allow for rotation of the legs 6 of the anchor rod 2 upon installation, as suggested by adhesive manufacturers. It is a further object to provide for adjustment of an anchor rod arrangement to the finished, correct elevation relative to the underdrain before backfilling with grout.